Maple syrup production involves drilling holes into (i.e., “tapping”) maple trees, collecting the sap that exudes from the wound, and then reducing or “sugaring” down the sap using reverse osmosis and evaporators to form the final syrup. Details of maple syrup production are described in the publication entitled “North American Maple Syrup Producers Manual” (second edition), produced by Ohio State University, in cooperation with the North American Maple Syrup Council, and edited by Heiligmann, Koelling and Perkins, which is incorporated by reference herein by way of background information.
The traditional way of collecting maple sap uses buckets at the tap source. The sap is then collected in a tank and then transported to the “sugarhouse” for processing. Over the years, a variety of specialized hardware has been developed for this task, including both sap spouts and specialized sap collection buckets or bags. For many years, however, the basic techniques of maple syrup and sugar production remained essentially unchanged.
More recently, modern syrup producers have replaced the traditional bucket collection system with a tubing system that includes special spouts (usually 5/16″ or 7/16″ diameter) and plastic tubing “droplines” (usually 5/16″ diameter and about 18″ to 36″ in length) connected to the various spouts. The droplines are then connected to lateral lines (also usually formed from 5/16″ diameter plastic tubing) that run between different maple trees. The lateral lines are in turn connected to one or more “main lines” (usually ¾″ to 2″ diameter) that run to the sugar house. Such systems are described in, for example, U.S. Pat. Nos. 2,877,601, 2,944,369, 3,046,698, and 3,057,115, and may either be gravity fed or utilize a vacuum pump to move the sap to a central collection point (e.g., an evaporator in the sugarhouse).
The sap flows from the tree through the spout and then through the line system when the pressure within the tree is greater than that in the lines. The line system then conveys the sap to the evaporator. To facilitate the extraction and transportation of the sap from the tree and to the evaporator, some systems use a pump to pull a vacuum within the line system. This increases the pressure differential between the inside of the line system and the tree, thereby increasing the volume of sap flow as compared to that which would naturally occur by gravity.
One of the main problems with such a vacuum-based system is the risk of microbial contamination of the taphole. The taphole formed in the tree is a wound. When a tree is wounded, microbes found in the environment (primarily Pseudomonas spp.) may colonize the taphole, thereby initiating a natural wound response and the process of “drying out,” which is an industry term for the cessation of sap flow. Thus, once sap exits the tree and becomes contaminated by microbes, it should not be allowed to remain at the taphole or flow back into the tree. If the sap is allowed to move back into the tree, or if the taphole is open to the air within the tubing lines, the microbes will more readily colonize the taphole, initiate the wound-response process, and cause the taphole to dry out and cease yielding sap.
The droplines presently used in gravity-based maple syrup production systems help reduce sap backflow. However, in vacuum-based systems, due to the larger pressure gradient, droplines do not adequately prevent sap backflow when the vacuum is interrupted.